A cold-induced color-changing thermal insulation organic hydrogel, and a preparation method and application thereof
By preparing a cryochromic and heat-insulating organic hydrogel of acrylic monomer and modified monomer in a mixed system of water and polyethylene glycol, the problem of high freezing point of existing thermochromic hydrogels is solved, achieving color change and antifreeze effects at low temperatures. It is suitable for buildings and insulation cabinets in low-temperature areas, reducing energy consumption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2024-02-23
- Publication Date
- 2026-06-19
AI Technical Summary
Existing thermochromic hydrogels have a high freezing point and a narrow range of applications. They cannot effectively suppress the leakage of heat radiation at low temperatures, resulting in high energy consumption in buildings and equipment such as insulated cabinets in low-temperature regions.
Acrylic monomers and modified monomers are reacted and crosslinked in a mixture of water and polyethylene glycol under the action of crosslinking agents, initiators, and catalysts to form a thermostatic organic hydrogel with cold-induced color change. By adjusting the ratio of water to polymer and the molecular weight ratio, the freezing point of the gel is significantly reduced and the gel's color-changing ability is achieved, meeting specific work requirements and application scenarios.
It has adaptive color-changing ability in low-temperature environments, can block heat radiation from passing through, has high transparency and freeze resistance, and is suitable for buildings and insulation cabinets in low-temperature areas, saving energy consumption.
Smart Images
Figure CN117986785B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of color-changing materials technology, and in particular to a thermochromic organic hydrogel, its preparation method, and its application. Background Technology
[0002] my country has a vast territory, a large north-south span, and a wide range of altitudes. Different regions have significant climatic characteristics and temperature differences, and the flow of goods between different regions needs to take into account the temperature effects on the products themselves.
[0003] For example, tropical and subtropical fruits are prone to irreversible frost damage when transported to high-latitude, high-altitude regions during winter; the extreme diurnal temperature variations in deserts and other areas also pose a significant challenge to fresh produce. In cold conditions, the heat loss from transparent insulated display cases used in construction and retail is primarily concentrated in the glass windows—areas prone to heat exchange. High-temperature objects inside the display case constantly radiate infrared radiation, which, after diffuse reflection and refraction, mostly escapes through the glass windows, resulting in substantial heat loss.
[0004] Therefore, suppressing heat radiation escape to the outside is an effective method of heat preservation. For example, emergency thermal insulation and lifesaving aluminum foil clothing utilizes the heat radiation reflection effect of aluminum foil on the human body, keeping the body temperature constant within a certain range. Improving the heat radiation blocking rate is of great significance for buildings and insulated cabinets in low-temperature areas, as it can improve the temperature stability of the internal environment and reduce the electrical energy consumed to maintain the temperature.
[0005] Existing technologies employ double or even multiple layers of glass, using air layers for thermal buffering to suppress heat exchange between the inside and outside. However, this approach cannot prevent the leakage of heat radiation. Furthermore, electrochromic materials require additional electrical energy to regulate the intensity of heat radiation exchange, which contradicts the goals of energy conservation and emission reduction.
[0006] Chinese patent CN112279945A discloses a thermochromic hydrogel-type smart window, comprising the preparation of a thermochromic hydrogel. This thermochromic hydrogel is prepared from maleic anhydride-modified chitosan, N-isopropylacrylamide (NIPAM), and cations of different valence states, with a phase transition temperature range of 20℃ to 70℃. This thermochromic hydrogel is a thermosensitive hydrogel, meaning it is transparent at low temperatures and colored at high temperatures.
[0007] Currently, most thermochromic hydrogels are thermochromic. For example, Chinese patent document CN113896908A discloses a method for preparing a composite hydrogel, which includes the following steps: mixing thermosensitive cellulose sol, acrylic acid, initiator, crosslinking agent and accelerator and then reacting them to obtain a composite hydrogel.
[0008] Existing thermochromic hydrogels have relatively high freezing points and limited applicability. Therefore, developing a cryochromic material that exhibits adaptive color-changing capabilities at low temperatures, high light transmittance, freeze resistance, and the ability to block heat radiation (i.e., transparent at high temperatures and colored at low temperatures) is of great significance for reducing the power consumption of temperature-controlled equipment such as buildings and insulated cabinets in low-temperature regions. Summary of the Invention
[0009] This invention provides a cold-sensitive color-changing heat-insulating organic hydrogel and its preparation method. The heat-insulating organic hydrogel has the advantages of high transparency, flexibility, and freeze resistance, and can inhibit heat radiation by cold-sensitive color change in low-temperature environments.
[0010] The technical solution of the present invention is as follows:
[0011] A thermochromic thermal insulating organic hydrogel is formed by reacting and crosslinking acrylic monomers and modified monomers in a mixed system of water and polyethylene glycol under the action of crosslinking agent, initiator and catalyst.
[0012] In the mixture of water and polyethylene glycol, the volume ratio of water to polyethylene glycol is 10 to 1:1;
[0013] The molecular weight range of polyethylene glycol is 200 to 1000.
[0014] In a mixture of water and polyethylene glycol, the freezing point of the gel can be significantly reduced, and the hydrogen bonding between water and polyethylene glycol enables the gel system to change color within a specified temperature range, thus meeting specific operational requirements and application scenarios. The mixing ratio of acrylic monomers and modified monomers can further precisely control the color-changing temperature of the glass, thereby satisfying the applicability of organic hydrogels at low temperatures. This provides a suitable color-changing material for temperature-controlled equipment such as buildings and insulated cabinets in low-temperature regions to regulate internal temperature and save energy consumption.
[0015] In a water-polyethylene glycol (PEG) mixture, as the proportion of PEG increases, the color change temperature and freezing temperature of the product decrease. If the water proportion is too high, the freezing temperature is not low enough, which is detrimental to the product's freeze-thaw resistance. If the PEG proportion is too high, the color change temperature is too low, which is also detrimental to the color change. To balance the color change temperature and freezing temperature, the amount of PEG added needs to be controlled within a reasonable range.
[0016] Preferably, in the mixture of water and polyethylene glycol, the volume ratio of water to polyethylene glycol is 5 to 1:1.
[0017] As the molecular weight of polyethylene glycol (PEG) increases, the color change temperature of the product gradually decreases, but the freezing temperature gradually increases. Excessively high molecular weight will cause the product's freezing temperature to exceed the applicable range, rendering it no longer freeze-resistant, while excessively low molecular weight will cause the color change temperature to exceed the applicable temperature range. Therefore, the selection of PEG molecular weight needs to be considered comprehensively.
[0018] Preferably, the molecular weight of polyethylene glycol is 200 to 600.
[0019] Preferably, the amount of acrylic monomer added is 3-20% based on the weight of the thermal insulation organic hydrogel.
[0020] The optimal addition amount of acrylic monomer is 6% based on the weight of the thermal insulation organic hydrogel.
[0021] Preferably, the modified monomer is one or more of acrylonitrile, N-vinylcaprolactam, and acrylamide.
[0022] Adjusting the ratio of acrylic monomer to modified monomer can precisely regulate the color change temperature of thermal insulation organic hydrogels within a small range, thereby improving the applicability of thermal insulation organic hydrogels in various applications.
[0023] More preferably, the mass ratio of acrylic monomer to modified monomer is 3:1 to 9.
[0024] Preferably, the modified monomer is acrylamide; the mass ratio of acrylic acid monomer to modified monomer is 3:7-8.
[0025] More preferably, the modified monomer is acrylamide; the mass ratio of acrylic acid monomer to modified monomer is 3:7.3-7.7.
[0026] Preferably, the modified monomer is acrylonitrile; the mass ratio of acrylic acid monomer to modified monomer is 3:1 to 2.
[0027] More preferably, the modified monomer is acrylonitrile; the mass ratio of acrylic acid monomer to modified monomer is 3:1.5 to 1.8.
[0028] Preferably, the modified monomer is N-vinylcaprolactam; the mass ratio of acrylic monomer to modified monomer is 3:2 to 3.
[0029] More preferably, the modified monomer is N-vinylcaprolactam; the mass ratio of acrylic monomer to modified monomer is 3:2.5-3.
[0030] Preferably, the crosslinking agent is N,N-methylenebisacrylamide; based on the weight of the thermal insulation organic hydrogel, the amount of crosslinking agent added is 0.9-9‰; more preferably 1.2-1.4‰.
[0031] Preferably, the initiator is ammonium persulfate; the catalyst is tetramethylethylenediamine and / or sodium bisulfite.
[0032] Based on the weight of the thermal insulation organic hydrogel, the amount of initiator added is 0.8-8‰; the amount of catalyst added is 0.9-9‰ by weight.
[0033] More preferably, based on the weight of the thermal insulation organic hydrogel, the amount of initiator added is 1.2 to 1.4‰, and the weight ratio of catalyst added is 1.2 to 1.4‰.
[0034] A preferred technical solution is as follows:
[0035] The thermochromic organic hydrogel is formed by the cross-linking of acrylic monomers and modified monomers in a mixed system of water and polyethylene glycol under the action of cross-linking agents, initiators and catalysts.
[0036] In the mixture of water and polyethylene glycol, the volume ratio of water to polyethylene glycol is 10 to 1:1;
[0037] The molecular weight range of polyethylene glycol is 200–600;
[0038] Acrylonitrile, N-vinylcaprolactam, and acrylamide are one or more of the following: the crosslinking agent is N,N-methylenebisacrylamide; the initiator is ammonium persulfate; and the catalyst is tetramethylethylenediamine and / or sodium bisulfite.
[0039] The mass ratio of acrylic monomer to modified monomer is 3:1 to 9;
[0040] Based on the weight of the thermal insulation organic hydrogel, the amount of acrylic monomer added is 5-10%.
[0041] The preferred technical solution uses an insulating organic hydrogel with a low freezing point and color change temperature, exhibiting good frost resistance, high transparency, and flexibility. It provides a suitable color-changing material for buildings and temperature-controlled equipment such as insulated cabinets in low-temperature regions to regulate internal temperature and save energy consumption.
[0042] This invention also provides a method for preparing the aforementioned heat-insulating organic hydrogel, comprising the following steps:
[0043] (1) Dissolve the N-isoacrylate monomer and the modified monomer in a mixture of water and polyethylene glycol in a certain proportion;
[0044] (2) Add crosslinking agent and initiator to the solution in step (1); then add catalyst to start chemical crosslinking reaction, and the reaction system is gelled to obtain the product.
[0045] Preferably, the temperature of the chemical cross-linking reaction is 30–60°C.
[0046] Preferably, the chemical cross-linking reaction takes 0.5 to 10 hours; more preferably 3 to 5 hours.
[0047] The thermal insulation organic hydrogel of the present invention has a freezing point as low as -20°C and has good antifreeze properties, and can be used to fill the double-glazed windows of thermal cabinets.
[0048] The present invention also provides a thermochromic, heat-insulating organic hydrogel-type smart window, comprising the aforementioned heat-insulating organic hydrogel.
[0049] Preferably, the thermochromic insulating organic hydrogel smart window comprises at least two layers of glass, with the insulating organic hydrogel sandwiched between the two layers of glass.
[0050] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0051] (1) The thermal insulation organic hydrogel of the present invention uses a mixture of water and polyethylene glycol as a continuous medium, and has the characteristics of low temperature resistance and cold-induced color change. It has high light transmittance above the color change point and can change color at low temperature, and has a wide range of applications.
[0052] (2) The thermal insulation organic hydrogel of the present invention does not require external additional energy consumption during the process of cold-induced color change, which is in line with the environmental protection concept of energy conservation and emission reduction.
[0053] (3) The concentration of acrylic acid and modified monomers within a certain range can effectively regulate the cold-induced color change temperature of the heat-insulating organic hydrogel, and has good applicability to working conditions.
[0054] (4) The thermal insulation organic hydrogel of the present invention has a short preparation cycle, simple production process, is suitable for large-scale production, and its unique flexibility enables it to play a role in various applications. Attached Figure Description
[0055] Figure 1 This is a schematic diagram illustrating the color change of the cryochromic insulating organic hydrogel located in the glass interlayer in this invention.
[0056] Figure 2 The transmittance (A) of the organic hydrogel product prepared in Example 2 at -10℃ and 20℃ in the range of 200-2500 nm, and the infrared diffuse reflectance (B) at -10℃ in the range of 2.5-25 μm.
[0057] Figure 3 The heat flow data for the cold-sensitive color-changing heat-insulating organic hydrogel are shown in (A) to (C), which correspond to the organic hydrogel products prepared in Examples 1 to 3, respectively.
[0058] Figure 4 The rheological test data are for the cold-sensitive color-changing heat-insulating organic hydrogels prepared in Examples 2, 5, 8 and Comparative Example 1.
[0059] Figure 5 The results of the simulation test show that the organic hydrogel product prepared in Example 2 was used as a glass interlayer in the window covering of a small insulated cabinet, and a single-layer glass was used as a control test.
[0060] Figure 6 The gel quality retention data are obtained by repeatedly switching between -20°C and 30°C 100 times in an open environment for the products prepared in Example 2 and Comparative Example 1.
[0061] Figure 7 The images show (A) of water and polyethylene glycol at a volume ratio of 1:0.8 at -20°C and (B) of pure water at -20°C.
[0062] Figure 8 These are actual images of the products of Comparative Examples 2(A), 3(B), 4(C), and 5(D) when inverted.
[0063] Figure 9 The images show the actual products obtained in Comparative Example 6 at -20℃ (A) and 30℃ (B). The products are transparent and do not change color at both temperatures.
[0064] Figure 10 The images show the physical products obtained in Comparative Example 7 (A) and Comparative Example 8 (B and C). The product obtained in Comparative Example 7 has strong fluidity, while the product obtained in Comparative Example 8 has lost its color-changing properties.
[0065] Figure 11 The curves show the trend of the color change temperature of the products obtained in Examples 10-15 as a function of the volume ratio of water and polyethylene glycol with a molecular weight of 400.
[0066] Figure 12 The curves show the trend of the freezing temperature of the products obtained in Examples 10-15 as a function of the volume ratio of water and polyethylene glycol with a molecular weight of 400. Detailed Implementation
[0067] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.
[0068] Test method:
[0069] 1. The transmittance of the organic hydrogel was measured using an in-situ variable-temperature ultraviolet spectrometer, with a measurement range of 300-2500 nm. The test temperatures were set at -10℃ and 30℃, with a measurement step of 1 nm. The visible transmittance of the organic hydrogel was calculated using the following formula:
[0070]
[0071] T lum It is the transmittance visible to the human eye, φ lum λ is the transmittance in the visible light wavelength range, T is the luminous efficiency function, and λ is the wavelength.
[0072] 2. The near-infrared absorptivity and diffuse reflectance of the organic hydrogel were measured using a Fourier transform infrared spectroscopy system. The measurements were conducted in diffuse reflectance and transmittance modes, with a step size of 2 cm. -1 The test range is 2.5–25 μm.
[0073] 3. The thermodynamic changes during the color change of the organic hydrogel were determined by differential scanning calorimetry to determine its color change temperature. The scanning temperature was reduced from 20℃ to -15℃ and then increased back to 20℃, with a scanning rate of 3℃ / min.
[0074] 4. The flexibility of the organic hydrogel was tested using an advanced intelligent rotational rheology system. The test mode was oscillating strain-shear mode, with the strain range set to 0.01–100%. The test frequency and temperature were 1 Hz and 20 °C, respectively.
[0075] 5. Application test of organic hydrogel in glass interlayer: The organic hydrogel was encapsulated in two pieces of ordinary glass and used as the cover window of the heat preservation cabinet. The heat preservation cabinet was placed in an environment of -20℃ and the internal and external temperatures were recorded.
[0076] 6. Cyclic testing of organic hydrogels: The organic hydrogels were subjected to cyclic switching tests at different temperatures in an exposed environment, with the cyclic temperature points being -20℃ and 20℃. The quality was tested after each cycle.
[0077] Examples 1-3
[0078] A method for preparing a thermostatic organic hydrogel with cold-sensitive color change includes the following steps:
[0079] (1) Mix water and polyethylene glycol with a molecular weight of 400 at a volume ratio of 1:0.8 to obtain a homogeneous organic aqueous solution, and take 5 mL for later use.
[0080] (2) Add 300 mg of acrylic acid and 730 mg (Example 1), 750 mg (Example 2), and 770 mg (Example 3) of acrylamide to 5 mL of organic aqueous solution and stir until completely dissolved.
[0081] (3) Add 8 mg of N,N-methylenebisacrylamide and 8 mg of ammonium persulfate to the resulting solution and stir to dissolve.
[0082] (4) Add 9 μL of tetramethylethylenediamine and quickly transfer the mixed solution to a mold at 40°C for 3 hours to carry out chemical reaction gelation, thus obtaining the final cold-sensitive color-changing heat-insulating organic hydrogel product.
[0083] The obtained organic hydrogel was tested, and the results are as follows:
[0084] Figure 2 The transmittance of the organic hydrogel prepared in Example 2 in the 200–2500 nm wavelength range at 20°C and -10°C is shown. At -10°C, the organic hydrogel exhibits good blocking effect for ultraviolet, visible, and infrared light in the 200–2500 nm wavelength range. At 20°C, the organic hydrogel has high transmittance in the visible light range, demonstrating high transmittance; calculations show that its transmittance visible to the human eye is greater than 91%. For infrared light in the 2.5–25 μm range, the organic hydrogel exhibits a certain degree of diffuse reflection after color change, significantly trapping internal heat radiation within the internal space and preventing heat radiation leakage, thereby maintaining internal temperature stability.
[0085] Figure 3 Differential scanning calorimetry (DSC) data for the prepared organic hydrogels are shown, with (A)-(C) corresponding to the organic hydrogel products prepared in Examples 1-3, respectively. The chemically synthesized cryochromic thermochromic organic hydrogels exhibited different color-changing temperatures at different acrylamide addition amounts, approximately 0°C, 5°C, and 10°C, respectively. Therefore, appropriately adjusting the amount of modified monomer added helps to precisely control the color-changing temperature of the cryochromic organic hydrogel. Furthermore, no other heat flow peaks appeared between -15°C and 0°C, indicating that the gel possesses certain antifreeze properties and can lower the freezing point of the system at low temperatures.
[0086] Figure 4 The rheological scanning data of the prepared organic hydrogel are shown in Example 2. The organic hydrogel prepared in Example 2 can achieve an elastic modulus (G') of nearly 5000 Pa and a viscous modulus (G”) of 950 Pa. Since its elastic modulus is greater than its viscous modulus, the organic hydrogel has semi-solid characteristics and a certain degree of elasticity, i.e., a certain degree of flexibility. The organic hydrogel product can maintain linear viscoelasticity within a 100% strain range. Therefore, its structure is not easily destroyed and can ensure that the cold-induced color-changing organic hydrogel can deform within a certain range.
[0087] Figure 5The data shows the temperature fluctuation of the organic hydrogel-laminated glass prepared in Example 2 as a cover window of a small insulated cabinet in an extremely cold environment over one day. Compared with single-layer glass, the organic hydrogel-laminated glass can raise the internal temperature of the insulated cabinet more quickly in the initial heating stage, and the temperature fluctuation range within the constant temperature range is smaller, thus providing a more temperature-stable storage space. Compared with the control group covered by single-layer glass, the insulated cabinet covered by organic hydrogel-laminated glass has a higher constant temperature under the same power consumption heater. This means that organic hydrogel-laminated glass as a window cover for the insulated cabinet has better energy-saving effect and helps to reduce the power consumption of the insulated cabinet.
[0088] Figure 6 The figure shows the mass change of the organic hydrogel prepared in Example 2 after 100 high and low temperature cycles under environmental exposure conditions. After 100 cycles, the mass retention rate of the organic hydrogel can still be maintained at more than 95%, which means that the organic hydrogel will achieve higher cycling performance in a closed environment and can play a greater role as a glass interlayer.
[0089] Figure 7 The results show that the mixture of water and polyethylene glycol can remain stable at a low temperature of -20°C without freezing.
[0090] Comparative Example 1
[0091] The solution system in step (1) of Example 2 was adjusted by replacing the mixture of water and polyethylene glycol with pure water, while keeping the other steps the same as in Example 2, to obtain a common hydrogel product.
[0092] Through testing, it was found that Figure 4 The modulus of the pure water system group decreased significantly during the strain scan, indicating that a certain intensity of shear strain can cause some damage to the gel structure. Therefore, the gel structure of the pure water system has poor stability.
[0093] Figure 6 Cyclic testing data of ordinary hydrogels showed that the system retained only 15% of its mass after 100 cycles, indicating that the pure water system has poor recyclability.
[0094] Figure 7 The actual image shows that pure water will freeze significantly at -20℃, which is not conducive to practical applications.
[0095] Comparative Example 2
[0096] In Example 2, the acrylamide in step (2) was adjusted to 100 mg, while other steps remained the same as in Example 2. The resulting product was as follows: Figure 8 As shown, it does not have a certain gelling ability and has strong fluidity, which is not conducive to fixation in a mold.
[0097] Comparative Example 3
[0098] Adjust the N,N-methylenebisacrylamide in step (3) of Example 2 to 1 mg, while keeping other steps consistent with Example 2. The resulting product is as follows: Figure 8 As shown, it does not have a certain gelling ability and has strong fluidity, which is not conducive to fixation in a mold.
[0099] Comparative Example 4
[0100] Adjust the ammonium persulfate in step (3) of Example 2 to 1 mg, while keeping other steps consistent with Example 2. The resulting product is as follows: Figure 8 As shown, it does not have a certain gelling ability and has strong fluidity, which is not conducive to fixation in a mold.
[0101] Comparative Example 5
[0102] Adjust the tetramethylethylenediamine in step (4) of Example 2 to 1 mg, while keeping other steps consistent with Example 2. The resulting product is as follows: Figure 8 As shown, it does not have a certain gelling ability and has strong fluidity, which is not conducive to fixation in a mold.
[0103] Comparative Example 6
[0104] In Example 2, the amount of modified monomer acrylamide added in step (2) was adjusted to 0 mg, while other steps remained the same as in Example 2. The resulting product was as follows: Figure 9 As shown, it is transparent at -20℃ and 30℃, and loses its ability to change color within this temperature range.
[0105] Comparative Examples 7-8
[0106] In Example 2, the amount of acrylic acid in step (2) was adjusted to 10 mg (Comparative Example 7) and 3000 mg (Comparative Example 8), while other steps remained the same as in Example 2. The product obtained in Comparative Example 7 was as follows: Figure 10 As shown in Example A, it lacks sufficient gel-forming ability and exhibits strong fluidity, making it unsuitable for fixation in a mold. The product obtained in Comparative Example 8, due to its high network density, cannot achieve complete color change. Figure 10 (As shown in B and C). Therefore, too little acrylic acid is not conducive to gel formation, while too much is not conducive to the color change effect of the product.
[0107] Examples 4-6
[0108] A method for preparing a thermostatic organic hydrogel with cold-sensitive color change includes the following steps:
[0109] (1) Mix water and polyethylene glycol with a molecular weight of 400 at a volume ratio of 1:0.8 to obtain a homogeneous organic aqueous solution, and take 5 mL for later use.
[0110] (2) Add 300 mg of acrylic acid and 165 mg (Example 4), 170 mg (Example 5), and 175 mg (Example 6) of acrylonitrile to 5 mL of organic aqueous solution and stir until completely dissolved.
[0111] (3) Add 8 mg of N,N-methylenebisacrylamide and 8 mg of ammonium persulfate to the resulting solution and stir to dissolve.
[0112] (4) Add 9 μL of tetramethylethylenediamine and quickly transfer the mixed solution to a mold at 40°C for 3 hours to carry out chemical reaction gelation, thus obtaining the final cold-sensitive color-changing heat-insulating organic hydrogel product.
[0113] The resulting organic hydrogel was subjected to rheological property testing, such as... Figure 4 As shown, the organic hydrogel G' prepared in Example 5 is greater than G”, and basically maintains linear viscoelasticity within the 100% strain range. Therefore, it has certain semi-solid characteristics and certain shear resistance. It has good structural stability and is not easily damaged by strain shear, and has a wide range of applications.
[0114] Examples 7-9
[0115] A method for preparing a thermostatic organic hydrogel with cold-sensitive color change includes the following steps:
[0116] (1) Mix water and polyethylene glycol with a molecular weight of 400 at a volume ratio of 1:0.8 to obtain a homogeneous organic aqueous solution, and take 5 mL for later use.
[0117] (2) Add 300 mg of acrylic acid and 280 mg (Example 7), 290 mg (Example 8), and 300 mg (Example 9) of N-vinylcaprolactam respectively to 5 mL of organic aqueous solution and stir until completely dissolved.
[0118] (3) Add 8 mg of N,N-methylenebisacrylamide and 8 mg of ammonium persulfate to the resulting solution and stir to dissolve.
[0119] (4) Add 9 μL of tetramethylethylenediamine and quickly transfer the mixed solution to a mold at 40°C for 3 hours to carry out chemical reaction gelation, thus obtaining the final cold-sensitive color-changing heat-insulating organic hydrogel product.
[0120] The resulting organic hydrogel was subjected to rheological property testing, such as... Figure 4As shown, the organic hydrogel G' prepared in Example 8 is greater than G” and basically maintains linear viscoelasticity within a 100% strain range. Therefore, it has certain semi-solid characteristics and certain shear resistance. It has good structural stability and is not easily damaged by strain shear, and has a wide range of applications.
[0121] Examples 10-15
[0122] In Example 2, the volume ratio of water to polyethylene glycol with a molecular weight of 400 in step (1) was adjusted to 10:0 (Example 10), 9:1 (Example 11), 8:2 (Example 12), 7:3 (Example 13), 6:4 (Example 14), and 5:5 (Example 15), while other steps remained the same as in Example 2. The resulting product color change temperature changes as follows: Figure 11 As shown, as the proportion of polyethylene glycol increases, the color change temperature of the product continuously decreases. Figure 12 The figure shows the freezing temperatures of the product. As the proportion of polyethylene glycol (PEG) increases, the freezing temperature of the product continuously decreases. When the proportion of water is too high, the freezing temperature of the product is not low enough, which is detrimental to the product's antifreeze properties, and the color change temperature is too high, which is also unfavorable for color-changing applications. When the proportion of PEG is too high, the color change temperature of the product is too low, which is also unfavorable for color change. To balance the color change temperature and freezing temperature of the product, the amount of PEG added needs to be controlled within a reasonable range.
[0123] Examples 16-18
[0124] In Example 2, the molecular weight of polyethylene glycol in step (1) was adjusted to 200 (Example 16), 600 (Example 17), and 800 (Example 18), while other steps remained the same as in Example 2. The resulting products had color-changing temperatures of 9°C (Example 16), 2°C (Example 17), and -6°C (Example 18), and freezing temperatures of -47°C (Example 16), -22°C (Example 17), and -14°C (Example 18), respectively. As the molecular weight of polyethylene glycol increases, the color-changing temperature of the product gradually decreases, but the freezing temperature gradually increases. Excessively high molecular weight can cause the product's freezing temperature to exceed the applicable range, thus rendering the product no longer freeze-resistant, while excessively low molecular weight can cause the product's color-changing temperature to exceed the applicable temperature range. Therefore, the selection of the polyethylene glycol molecular weight needs to be considered comprehensively.
[0125] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A thermochromic, heat-insulating organic hydrogel, characterized in that, It is formed by the cross-linking of acrylic monomers and modified monomers in a mixed system of water and polyethylene glycol under the action of cross-linking agents, initiators and catalysts; In the mixture of water and polyethylene glycol, the volume ratio of water to polyethylene glycol is 10 to 1:
1. The molecular weight range of polyethylene glycol is 200 to 1000; Based on the weight of the thermal insulation organic hydrogel, the amount of acrylic monomer added is 3-20%; The modified monomer is one or more of acrylonitrile, N-vinylcaprolactam, and acrylamide; the mass ratio of acrylic acid monomer to modified monomer is 3:1~9; The crosslinking agent is N,N-methylenebisacrylamide; Based on the weight of the thermal insulation organic hydrogel, the amount of crosslinking agent added is 0.9~9‰; The initiator is ammonium persulfate; the catalyst is tetramethylethylenediamine and / or sodium bisulfite; based on the weight of the heat-insulating organic hydrogel, the amount of initiator added is 0.8-8‰; the amount of catalyst added is 0.9-9‰ by weight.
2. The thermochromic thermal insulating organic hydrogel according to claim 1, characterized in that, It is formed by the cross-linking of acrylic monomers and modified monomers in a mixed system of water and polyethylene glycol under the action of cross-linking agents, initiators and catalysts; In the mixture of water and polyethylene glycol, the volume ratio of water to polyethylene glycol is 10~1:1; The molecular weight range of polyethylene glycol is 200 to 600; The modified monomer is one or more of acrylonitrile, N-vinylcaprolactam, and acrylamide; the crosslinking agent is N,N-methylenebisacrylamide; the initiator is ammonium persulfate; and the catalyst is tetramethylethylenediamine and / or sodium bisulfite. The mass ratio of acrylic monomer to modified monomer is 3:1~9; Based on the weight of the thermal insulation organic hydrogel, the amount of acrylic monomer added is 5-10%.
3. A method for preparing the thermally insulating organic hydrogel as described in claim 1 or 2, characterized in that, Includes the following steps: (1) Dissolve the acrylic monomer and the modified monomer in a mixture of water and polyethylene glycol in a certain proportion; (2) Add crosslinking agent and initiator to the solution in step (1); then add catalyst to start chemical crosslinking reaction, and the reaction system is gelled to obtain the solution.
4. The method for preparing the thermally insulating organic hydrogel according to claim 3, characterized in that, The temperature for the chemical cross-linking reaction is 30~60°C; the reaction time is 0.5~10 h.
5. A thermochromic, heat-insulating organic hydrogel-based smart window, characterized in that, Including the thermally insulating organic hydrogel as described in claim 1 or 2.